/* 根元素 */
/* 变量 */
:root{
    --line-border-fill:#3498db;
    --line-border-empty:#c0c0c0;
}
*{
    box-sizing: border-box;
}
body{
    border-color: white;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    overflow: hidden;
    margin: 0;
}
.container{
    text-align: center;
}
.progress_container{
    display: flex;
    justify-content: space-between;
    position: relative;
    margin-bottom: 30px;
    max-width: 100%;
    width: 350px;
}
.progress_container::before{
    content: '';
    position: absolute;
    background-color: var(--line-border-empty);
    top:50%;
    left: 0;
    transform: translateY(-50%);
    height: 4px;
    width: 100%;
    /* 层级 */
    z-index: -1;
}
.progress{
    background-color: var(--line-border-fill);
    position: absolute;
    top:50%;
    left:0;
    transform: translateY(-50%);
    transition: all 0.8s ease;
    height: 4px;
    width: 0%;
    z-index: -1;
}
.circle{
    background-color: white;
    color:#c0c0c0;
    border-radius: 50%;
    width: 30px;
    height: 30px;
    display: flex;
    justify-content: center;
    align-items: center;
    border: 3px solid var(--line-border-empty);
    transition: all 0.8s ease;
}
.active{
    border-color: var(--line-border-fill);
}
.btn:active{
    transform: scale(0.98);
}
.btn:focus{
    outline: 0;
}
.btn:disabled{
    background-color: var(--line-border-empty);
    cursor: not-allowed;
}